There is a continuing need for lighting apparatus which is low-cost and energy-efficient. LEDs (light-emitting diodes) provide light sources which are energy-efficient, and advances in LED technology are providing even greater efficiencies over time.
Some of the newer applications for LED-based lighting systems are roadway, street and parking-lot lighting. In such applications, there are desired performance characteristics with respect to light distribution. More specifically, it is desirable that certain regions about a light fixture be illuminated, while certain neighboring regions are essentially non-illuminated. Along roadways and in parking lots, there is a need to be able to direct light in a particular preferential lateral direction (e.g., to illuminate a roadway) while avoiding so-called “trespass light” in an opposite lateral direction (a non-preferential lateral direction), e.g., toward roadside houses.
Some efforts have been made to develop small lenses for directing light emitted by small LED packages, and utilizing lenses intended to redirect some amount of emitted light to one side preferentially. However, such lenses fall short of highly desirable performance with respect to avoiding trespass lighting. Some of such lenses are difficult and expensive to manufacture, which increases overall cost for LED lighting using such lenses.
The measure of trespass lighting includes more than just the amount of light energy falling toward the non-preferential side but also includes how far into the area on the non-preferential side that the light falls. It would be highly beneficial to provide a lighting apparatus which produces a desired illumination pattern with a maximum amount of emitted light toward an area intended to be illuminated and with improved uniformity of light distribution.